Lands and Mana Costs
Examples of Land Cards
The basic types of lands are Plains, Islands, Forests, Mountains, and Swamps, pictured respectively below.
Why Do You Need Land?
About a third of any deck (20-24 cards) should be lands, and the rest will be spells. You need land because each spell you want to play will cost you mana. Land cards generate 1 mana of a particular color when you tap it. When you tap a Plains, you generate a white mana; tapped Islands generate blue, tapped Forests generate green, tapped Mountains generate red, and tapped Swamps generate black.
Reading Mana Costs on Cards
To know how much mana you will need to play a spell, look up to the top right corner of each card--this is where the mana cost will be displayed. The symbols for each mana color are as follows:
Image retrieved from Wizards.com
Symbols from left to right: white mana, blue mana, black mana, red mana, green mana.
For example, look at the top right corner of the card shown below, called Elvish Spirit Guide:
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In the top right corner, it shows the number 2 in a gray circle, and beside it, there is 1 tree symbol. (Notice that the tree symbol on the Forest I showed you earlier is the same.) This means that in order to play Elvish Spirit Guide, you need 3 total mana; 1 mana has to be green (has to come from a Forest), and the other 2 mana can be any color. (When you see a number in a gray circle, it means that the spell takes that much colorless, or any type, of mana to play.) |
Some mana costs are a lot more complicated-looking, however. Check out Razia, Boros Archangel below:
 | Razia is an example of a multicolored card; she is both red and white. Thus, it takes mana of both colors to play her--and quite a lot of it, too! There are two Plains symbols and two Mountain symbols in her cost, telling us that it takes at least two white mana and two red mana to play her. The 4 in the gray circle tells us that it also takes 4 mana of any color to play her. All totaled, Razia costs 8 mana to play. |
But what about cards that don't have any colorful mana symbols in their cost, like Platinum Angel, shown here?
 | All that shows up in the top right corner is the number 7 in a gray circle. Remember that a number in a gray circle means that it takes that much colorless mana to play. In this case, Platinum Angel takes 7 mana to play. But it doesn't have to be any particular color! Many artifacts are like this--most artifacts are made to be able to fit into many different kinds of decks, so often you will find artifacts with no color commitment in their cost (as in, you don't absolutely have to have a certain color of mana to play it). |
Other Ways Mana Costs Can Be Written
 Image from RedBubble | If you see a mana cost with symbols like the one at left, it simply means that one of either of those two colors of mana could be paid for this cost. These symbols are called "hybrid mana" symbols. For instance, the symbol at left means that either one red or one blue mana is needed. |
Image from MTG.com
This type of symbol means that either 2 of any color of mana or 1 of the specified color of mana is needed to pay this cost.
Image from MTG.com
This symbol, called "Phyrexian Mana", means that the cost can be paid with either 1 of the specified mana color, or with 2 life. Great for those times when you just don't have the colors you need, but you do have some Life Points you can spare!